1. Field of the Invention
The present invention relates to an endoscope including an observation optical system with wide viewing angle, and also relates to a method for repairing the endoscope.
2. Description of the Related Art
As is well-known, an endoscope is widely used in a medical field, and the like. The endoscope, for example, can provide observation of organs and the like within a body cavity by inserting an elongated insertion portion into the body cavity and various treatments using a treatment instrument inserted into a treatment instrument insertion channel as needed. A bending portion is formed at the distal end of the insertion portion, and the observation direction of an observation window at the distal end can be changed by operating an operation portion of the endoscope.
The conventional endoscope has an observation viewing angle of approximately 120 to 140 degrees, and an operator observes inside a body cavity with an observation image at the observation viewing angle. If the operator would like to observe a site outside a viewing field range during the observation in the body cavity, the operator observes the site by bending the bending portion.
Meanwhile, there have been proposed various endoscopes with wider observation viewing angle so as to observe a wider range.
For example, Japanese Patent Application Laid-Open No. 2001-258823 discloses an endoscope including at a distal end portion thereof an observation optical system with a wide observation viewing angle of approximately 140 to 210 degrees. In the endoscope disclosed in the publication, in accordance with the wider viewing angle of the observation optical system, a light guide fiber bundle for illuminating inside a body cavity is disposed such that the optical axis of a distal end portion of the bundle is inclined outwardly at a predetermined angle with respect to the optical axis of the observation optical system, in order to uniformly illuminate all over an observation site in the body cavity.
Incidentally, the light guide fiber bundle is connected as one fiber from a distal end of a universal cord connected to a light source device to an endoscope distal end portion in the endoscope. Therefore, when a part of the light guide fiber bundle is damaged, it is required to replace the whole of the light guide fiber bundle with a new one.
When replacing the light guide fiber bundle, an outer cover tube covering the endoscope distal end portion is removed at first, to expose the distal end portion of the light guide fiber bundle inserted inside the distal end portion of the endoscope, and then the distal end portion of the light guide fiber bundle fixed to a distal end rigid portion is detached by using a tool and the like. After that, the light guide fiber bundle is pulled out from the side of the universal cord. Next, a new light guide fiber bundle is inserted from the side of the universal cord, and a distal end of the bundle is attached to the distal end rigid portion by using a tool and the like, to be adhered and fixed thereto.